It's not often that a round of the Heineken Cup fails to stir the juices, but you can tell that round five is a little flat by the heavy promotion of the route for three pool runners-up into the Amlin Cup. While the two best second-placed teams – see how convoluted this can become – will go on their travels to away quarter-finals in the main tournament, the next best three runners-up will go into the last eight of the Amlin and one pool runner-up will wave goodbye to Europe for the season. It's not exactly the most compelling of sales pitches.

It's not that the Heineken Cup has gone completely off the boil. It's just that round five is the calm before six, the showdown round with everything at stake. Munster-Northampton, Ospreys-Leicester, London Irish-Leinster (at Twickenham) and either Sale-Toulouse or Cardiff Blues-Harlequins promise a rare weekend of resolution. Normally, Munster have these last-round dramas to themselves, but this time they just take their place in the mix.

Part of the trouble is that three French giants have their pools more or less under their control already. Stade Français may have been rolled over by Ulster at Ravenhill, with Ian Humphreys having a game to remember, but they recovered the following week in Paris and should see off Bath this Saturday.

Toulouse lost away in Cardiff to the Blues, but look unbeatable at home and have lowly Harlequins there before that last encounter away in Stockport to Sale. For that final fixture to make the pulse race, Sale must first beat the Blues in a game that would stand apart in round five for dramatic potential, were it not that the Blues at the very worst moment are becalmed. Memories of their riotous progress to the semi-final last season have faded to such an extent that the only news out of their camp concerns Xavier Rush's possible departure to Japan and Ben Blair mulling offers from France.

Biarritz, still all over the shop in France's Top 14, are models of consistency in pool 2, unbeaten and eight points ahead of second-placed Gloucester. They could afford to lose at Kingsholm on Saturday and wrap up a quarter-final at one home, San Sebastián, with a victory at another, the Parc des Sports Aguiléra, over Glasgow.

The French control half the pools and it could have been worse for the other competing nations. Perpignan are the reigning domestic champions of France and Clermont the club they beat in last season's Top 14 final. But Perpignan came completely unstuck on the first weekend, losing away at Treviso, and then committed an even worse act in the eyes of their demanding supporters by losing at home to Munster. And not just losing, but being overwhelmed by the Irish province at their ominous best.

Munster, apparently recovered from the shock of seeing the balance of Irish power shift Leinster's way, are away in Treviso on Saturday lunchtime. The complacency that caused Perpignan to drop their guard in Italy will not touch Munster as long as they are only second-best in Ireland. In fact, there are few grounds to suppose that Ireland are going to be anything but ferocious in all competitions.

The good news for the health of the Heineken competition is that Northampton present a formidable challenge in Munster's pool. From the moment they refused to capitulate, away at the Stade Aimé-Giral on the one night that Perpignan gave it their all, Northampton seem to be striding forward on all fronts, no longer a dangerous side on their day, but consistently powerful and confident of their ability to play in a variety of styles. They have a chance to test the resolve of Perpignan, who might regret declaring their interest in the H Cup over.

Only one pool has a three-team contest for top spot, No3, involving Clermont, the Ospreys and Leicester. The French club still think they control the destiny of the group, thanks to the losing bonus point they picked up away at Leicester, and with "only" the Ospreys at home and Viadana away to come.

Now, the Ospreys, dare it be whispered after years of flopping on the big day, are playing with a ruthless steeliness. They are still without Mike Phillips but are grinding out important wins, rather than losing in glam-rock confusion. They have to take their new Magners form to the Stade Marcel-Michelin in Clermont-Ferrand, but they could produce the result of the weekend, even if it yields nothing more than a bonus point in defeat. On such fine margins will pool 3 be decided.

Talking of playing with steel, Leicester are as dynamic as any club in Europe at the moment, their demolition of Wasps a masterclass in taking a hold up front and never relaxing the grip. On the eve of the Six Nations and with England-Wales on the opening Saturday, the clash between the Ospreys and the Tigers at the Liberty Stadium in round six could not be a better prologue. It might be more uninhibited than the full Test. Leicester's home tie to Viadana in round five is not quite as tingling.

That leaves pool 6 where there is almost as much at stake in a strange Irish cross-border sort of way. London Irish, by support if not player registration, are still very much an Irish experience and Leinster are very much the team of the year in the age of the Irish. So, when London meets Dublin there's going to be a showdown.

But not yet. That's for round six and there are obstacles to climb first, London Irish, for example, at the Scarlets, who produced the shock of the tournament so far by beating the Exiles in Reading straight after the same Irish won away at Leinster.

As for the defending champions, they recovered from that opening shock by thumping first Brive and then the Scarlets on the road. Brive at home now should be a formality. As is the theme, it's a round to tick off before the real excitement comes the weekend after. The Irish and the Irish at Twickenham. Perfect.

This is an extract from The Breakdown, Eddie Butler's weekly email on the world of rugby union. To subscribe click here